Catalog for the JBang command line launcher (https://jbang.dev)

To use the JBang scripts from this catalog you need to have JBang installed.

To start the Jython interpreter or run a Jython script via the interpreter, use JBang as follows and add additional options as required:

• jbang run jython-cli@jython <jython-script>.py

The jython-cli@jython JBang script can also be installed as a JBang application which is accessible from the command-line.

jbang app install jython-cli@jython
[jbang] Command installed: jython-cli

Jython scripts can be run using the jython-cli application as:

• jython-cli <jython-script>.py

On supported platforms a Jython script (with execution permissions enabled) can also be started as

./<jython-script>.py

provided that the first line of the script contains text:

#!/usr/bin/env jython-cli

jython-cli uses the PEP-723 inline script metadata format to specify:

• The version of Jython to use: 2.7.1, ...
• The major version of Java use: 17, 21, ...
• Maven dependencies to make available to the Jython script
• Additional Java runtime options to use

Jython metadata for JBang

# /// jbang
# requires-jython = "2.7.4"
# requires-java = "21"
# dependencies = [
#   "io.leego:banana:2.1.0"
# ]
# runtime-options = [
#   "-server",
#   "-Xmx2g",
#   "-XX:+UseZGC",
#   "-XX:+ZGenerational"
# ]
# ///

Jython script banner.py with metadata for JBang

#!/usr/bin/env jython-cli

# banner.py

# /// jbang
# requires-jython = "2.7.4"
# requires-java = "21"
# dependencies = [
#   "io.leego:banana:2.1.0"
# ]
# runtime-options = [
#   "-server",
#   "-Xmx2g",
#   "-XX:+UseZGC",
#   "-XX:+ZGenerational"
# ]
# ///

import sys

import io.leego.banana.BananaUtils as BananaUtils
import io.leego.banana.Font as Font

def main():
    print(sys.argv)

    text0 = "Jython 2.7"
    text1 = BananaUtils.bananaify(text0, Font.STANDARD)

    print(text1)

main()

Use the option --cli-debug to display the jbang metadata read from the script, and what it has been decoded into (as JSON).

PS jython-jbang-catalog> jbang jython-cli --cli-debug examples\banner.py
     5 :# /// jbang
     6 :# requires-jython = "2.7.4"
     7 :# requires-java = "21"
     8 :# dependencies = [
     9 :#   "io.leego:banana:2.1.0"
    10 :# ]
    11 :# runtime-options = [
    12 :#   "-Dpython.console.encoding=UTF-8"
    13 :# ]
    14 :# ///
{
  "requires-jython" : "2.7.4",
  "requires-java" : "21",
  "dependencies" : [
    "io.leego:banana:2.1.0"
  ],
  "runtime-options" : [
    "-Dpython.console.encoding=UTF-8"
  ],
}

[jbang.cmd, run, --java, 21, --runtime-option, -Dpython.console.encoding=UTF-8, --deps, io.leego:banana:2.1.0, --main, org.python.util.jython, org.python:jython-slim:2.7.4, examples\banner.py]
...

jbang run jython-cli@jython --version

Jython 2.7.4

jbang run jython-cli@jython -c "print(1+2)"

3

Using Java 21 (default)

jbang run jython-cli@jython

Jython 2.7.4 (tags/v2.7.4:3f256f4a7, Aug 18 2024, 10:30:53)
[OpenJDK 64-Bit Server VM (Eclipse Adoptium)] on java21.0.6
Type "help", "copyright", "credits" or "license" for more information.
>>> print(1+2)
3
>>> 

Using Java 8

jbang run --java 8 jython-cli@jython

Jython 2.7.4 (tags/v2.7.4:3f256f4a7, Aug 18 2024, 16:49:39)
[OpenJDK 64-Bit Server VM (Temurin)] on java1.8.0_452
Type "help", "copyright", "credits" or "license" for more information.
>>> 

Script banner.py is located in folder https://github.com/jython/jbang-catalog/examples.

jbang run jython-cli@jython banner.py

['banner.py']
      _       _   _                   ____   _____ 
     | |_   _| |_| |__   ___  _ __   |___ \ |___  |
  _  | | | | | __| '_ \ / _ \| '_ \    __) |   / / 
 | |_| | |_| | |_| | | | (_) | | | |  / __/ _ / /  
  \___/ \__, |\__|_| |_|\___/|_| |_| |_____(_)_/   
        |___/                                      

Script restclient.py is located in folder https://github.com/jython/jbang-catalog/examples.

jbang run jython-cli@jython restclient.py

{
  "userId": 1,
  "id": 1,
  "title": "delectus aut autem",
  "completed": false
}

Script turtle.py is located in folder https://github.com/jython/jbang-catalog/examples.

jbang run jython-cli@jython turtle.py

If the jython_cli.java program is modified and needs to be tested (before changes are submitted to the repo), the example scripts can be used as tests and run locally (using Java 21):

• jbang run jython-cli examples/banner.py
• jbang run jython-cli examples/restclient.py
• jbang run jython-cli examples/httpserver.py
• jbang run jython-cli examples/turtle.py
• jbang run jython-cli examples/simpletest.py

Also test the jython-cli script with Java 8:

• jbang run --java 8 jython-cli examples/banner.py
• jbang run --java 8 jython-cli examples/restclient.py
• jbang run --java 8 jython-cli examples/httpserver.py
• jbang run --java 8 jython-cli examples/turtle.py
• jbang run --java 8 jython-cli examples/simpletest.py

On Linux or MacOS the JythonCli.java script can be run directly for testing purposes:

• ./JythonCli.java -V
• ./JythonCli.java examples/banner.py

The following articles describe the work that led to the creation of the jython-cli JBang script.

• Medium.com - Running Jython scripts with JBang using a Java helper program (Part 1)
• Medium.com - Running Jython scripts with JBang using PEP 723 (Part 2)